Such a head simulator is used to evaluate communication systems. In addition to the designation “Kunstkopf” head simulator, the term, head and torso simulator or the acronym HATS for short, is used as well. The present application pertains to head simulators for respirators, which are equipped with communication systems.
A respirator has a breathing mask, and there are various types of respirators that differ from one another in the manner in which breathing air is supplied: Breathing of ambient air through a filter, supply of ambient air through a blower and a filter, and, in case of a compressed air breathing apparatus, supply of air from a compressed air cylinder through a demand oxygen system. The combination of breathing mask and air source leads to respirators that are designated in the American English usage as follows:—Air Purifying Respirator (APR): Breathing mask+filter;—Powered Air Purifying Respirator (PAPR): Breathing mask+blower filter; and—Self-Contained Breathing Apparatus (SCBA): Breathing mask+compressed air breathing apparatus.
These respirators differ for the user primarily by the protection factor provided. It is, however, common to all respirators that they more or less greatly impair the audibility and the intelligibility of the respirator user's speech.
Verbal communication is one of the most important types of communication. This may differ in terms of loudness, sound quality, delay, speech intelligibility and many other factors. Unobstructed communication is not always possible, which applies especially to users of respirators. Electronic communication systems are therefore used for support. Such a communication system comprises a microphone in the interior of the mask, which picks up the words spoken by the user of the respirator and reproduces them via a loudspeaker on the outer surface of the breathing mask. In addition or as an alternative, the picked-up microphone signals may also be transmitted in a wireless manner to a receiver and reproduced there via a loudspeaker or earphone. The use of speaker simulators, also called head simulator, is an already established procedure for evaluating and optimizing the efficiency of such communication systems. A communication system can thus be evaluated reproducibly and objectively. The test set-up in this case imitates the routine use very well and thus makes a meaningful evaluation possible. The head simulators therefore have a head simulator body with as natural a head shape as possible and in it a simulated oral cavity with simulated oral aperture, behind which a loudspeaker is installed as a sound source in the simulated oral cavity. The sound of the loudspeaker is emitted from the simulated oral aperture in a bundled form, and acoustic tests can thus be carried out on communication systems under reproducible conditions. Such a head simulator is, for example, the device 4128-C of the company Brüel & Kjaer, which has the features including a head simulator body with a simulated oral aperture, a simulated oral cavity, a loudspeaker and an audio unit connected to the loudspeaker for reproducing speech via the loudspeaker.
Oral communication plays a prominent role above all for fire departments, because direct and natural communication must function especially effectively here during rescue operations involving danger to life. Communication systems are needed especially urgently during rescue operations involving the use of respirators because the natural speech is markedly impaired due to the use of a breathing mask, which attenuates especially high-frequency components of speech. As was mentioned, prior-art communication systems for breathing masks have an integrated speech amplifier, which compensates the attenuation caused by the mask by the speech picked up by a microphone being reproduced in an amplified form by means of loudspeakers located on the outer side of the breathing mask. The speech intelligibility is improved in this manner.
A headset function for radio communication is often additionally integrated in a mask-based communication system. An analog or digital radio is connected for this to the mask-based communication system with a cable or a wireless interface (e.g., Bluetooth). Marked improvement is thus achieved compared with working with a hand-held radio due to the integration of the microphone for sending the voice signals in the mask. The received signal is played via an earphone in such systems.
The breath sounds occurring during the operation are likewise picked up by the microphone and reproduced by the loudspeakers in an amplified form. However, these breath sounds interfere with the communication and the microphone signals are therefore filtered by means of digital signal processing in a signal processor in the communication unit in order to suppress breath sounds and thus possibly not to reproduce them via the loudspeakers and not to transmit them by radio.
The optimization of precisely this functionality of breath sound suppression represents a challenge in connection with the development. A clear automatic separation between breath sounds and speech is essential here in order to make optimal, trouble-free communication possible.
The case of use to be optimized cannot satisfactorily be simulated by means of the above-described head simulators, which can only simulate the speech, because the head simulators can only reproduce the breath sounds by means of the loudspeaker, and these sounds differ greatly from real breath sounds. The evaluation of respirators with communication units is thus only possible relative to the speech, but it cannot be accomplished in such a way that the effects of the breathing of the respirator user are taken into consideration in a realistic manner.